The present invention relates to electrostatic precipitators and more particularly to a method and apparatus for monitoring and controlling tumbling hammer rappers.
Electric precipitators contain a plurality of electrodes for electrostatically removing particulate matter suspended in the gas passing therethrough. The particulate matter is attracted by and accumulates on the electrodes. A sufficient amount of particulate matter build-up causes a decrease in the efficiency of particulate matter removal as well as other detrimental effects. It is therefore necessary to clean the electrodes for particulate matter disposal and to maintain efficiency of particulate matter removal while minimizing the other detrimental effects of accumulated particulate matter on the electrodes.
A tumbler hammer type rapper is commonly used for removal of accumulated particulate matter from the collecting and discharge electrodes of electrostatic precipitators. In a tumbler hammer type rapper, each of the plurality of tumbling hammers is pivotally attached to a disk which in turn is rigidly attached to a rapper shaft. As the rapper shaft rotates through each revolution (one cycle), the hammers are first raised then fall under the force of gravity as they pivot on the disk and strike an anvil attached to either a collecting or discharge electrode, thereby vibrating the struck electrode causing the particulate matter accumulated thereon to fall into a collection hopper below.
One known method of cleaning the electrodes of an electrostatic precipitator is to periodically energize a drive unit to rotate the rapper shaft of the tumbler hammer type rapper. The drive unit is energized for a predetermined time period of sufficient duration to rotate the rapper shaft at least one revolution.
However, there is no feedback signal to indicate that indeed the rapper shaft has rotated. Therefore, a need exists for monitoring the rotation of a tumbler hammer type rapper shaft and providing a feedback signal to assure proper rotation. A further need exists to allow only one strike from each hammer for each cycle of operation of the tumbler hammer type rapper to minimize reentrainment of particulate matter. Should the tumbler hammer type rapper shaft fail to rotate, the feedback signal would be utilized to initiate an alarm indicating the tumbler hammer type rapper has malfunctioned.